In a conventional solid-state imaging device used for a digital still camera, etc., pixel signals obtained from respective pixels for photoelectric conversion are transferred to and stored in a storage portion, for example, in each row, and then the pixel signals of each row are output sequentially in synchronization with readout pulses output from a horizontal shift resistor (see, for example, FIGS. 13 and 14 of JP2001-45378A).
FIG. 7 shows configurations of a MOS type solid-state imaging device 8 (partially shown) and an external circuit 9 of a conventional example. The solid-state imaging device 8 includes a plurality of pixels 1 arranged two-dimensionally. Each pixel 1 is supplied with a selection signal for each row from a vertical shift resister 2. Vertical signal lines 3 in the direction of a column are connected to the pixels 1 of each column, respectively. Each vertical signal line 3 is connected to a row memory 4 in which signals in each row are stored. Each row memory 4 is respectively connected via a readout switch 14 to an output signal line 6 for outputting pixel signals of each row. The readout switch 14 is driven by an output of a horizontal shift resistor 5. The output signal line 6 is connected to an output amplifier 7 and the output therefrom is supplied to the external circuit 9. The external circuit 9 includes external memories 10 in which pixel signals output from the solid-state imaging device 8 are stored in each row and color selection switches 11.
In this solid-state imaging device 8, a plurality of pixels 1 are arranged in a Bayer arrangement of the three primary colors, red (R), green (G) and blue (B). Signals of the pixels 1 of each row are read out into the vertical signal line 3 in each row by the vertical shift resistor 2 and transferred to the row memory 4. The pixel signals stored in the row memory 4 are respectively read out through readout switches 14 sequentially in the order in which readout pulses S1 to S6 are output from the horizontal shift resistor 5, and output from the output amplifier 7 via the output signal line 6. Signals input in the external circuit 9 from the output amplifier 7 are switched for each color by a color selection switch 11 and stored in the external memory 10. Then, image processing is performed.
FIGS. 8A and 8B show output waveforms from the output amplifier 7 of the above-mentioned conventional MOS type solid-state imaging device. The pixel signals of the n-th row in the solid-state imaging device 8 shown in FIG. 7 are output as shown in FIG. 8A. According to sequential turning on of the readout pulses S1 to S6 from the horizontal signal transmission circuit 5, the signals of G2 (n), B (n), G2 (n), B (n), G2 (n) and B (n) are output in this order from the amplifier 7. Similarly, as shown in FIG. 8B, the output signals of the (n+1)-th row are output from the amplifier 7. The signals of R (n+1), G1 (n+1), R (n+1), G2 (n+1), R (n+1) and G1 (n+1) are output sequentially in this order. At this time, in the output signals from the output amplifier 7, pixel signals of different colors are adjacent to each other. Therefore, in the external circuit 9, it is necessary to sort output signals for each color by the color selection switch 11 at high speed so as to input them into the external memory 10 for each color. In the case of the configuration shown in FIG. 7, in order to transfer pixel signals of one row to the external memory 10, it is necessary to switch the color selection switch 11 six times. Therefore, with respect to pixel signals of one row of the n-th row and the (n+1) row, it is necessary to switch the color selection switches 11 twelve times.
Furthermore, since output signals tend to be influenced by the adjacent signal, colors may be mixed with each other, which may lead to a deterioration of the image quality. In particular, when the speed of outputting signals is increased, it is necessary to suppress the increase in the speed of the color signal selection switch 11 in the external circuit 9 and suppress the mixing of colors with each other.